This invention relates to a method and system for measuring the diameter and shape of an electron beam used in such electron beam devices as an apparatus for electron beam lithography.
The adjustment in the electron beam devices to keep the diameter minimum or the shape of the spot of the beam on the specimen circular is called a focus adjustment or astigmatism correction, respectively. In conventional methods of adjustment, an operator watches a cathode ray tube to measure the rise time of a detector signal which is obtained by having the electron beam sweep across a mark on the specimen at a boundary between two areas with different characteristics.
In scanning type electron microscopes, these adjustments may be performed directly by observing an image and adjusting it on the basis of the observer's visual sense. The conventional methods, however, have disadvantages in that the adjustment takes time and the accuracy thereof varies depending on the individual who works on the device, because the adjustment depends on the operator's judgment.